The present invention is directed to a front beam and tension rod arrangement for use with a push back storage rack system.
Push back storage rack systems normally comprise an assembly of shelves and interconnected front and interior vertical uprights for storing loads placed on tracks or other base members in one or more storage lanes. Each storage lane has one loading position capable of storing one load. One or more push back carts are positioned in the loading position. Each cart is capable of receiving one load and is positioned to be pushed toward the back of the lane by the next load. Such systems normally have their tracks in each lane tilted toward the loading position so that the force of gravity causes the next cart in line to return to the loading position when a load occupying the loading position is removed.
Most push back storage rack systems have a transversely positioned front beam placed in front of each lane""s loading position to provide structural support between the two most adjacent vertical uprights. The vertical positioning of each front beam is usually sufficiently low to allow for the addition of loads to each lane""s loading position. Due to this positioning, the front beams of most designs also serve to restrict downward cart movement once a cart enters the loading position. In most circumstances, a cart moving into the loading position from a higher track position bears substantial additional weight from its load. As a consequence, a front beam must withstand the combined sliding impact of both a cart and its load when the cart collides with the beam at the loading position.
During the operational life of most storage rack systems, each beam must withstand repeated collisions from loaded carts. The collisions tend to cause the front beam to flex outward, gradually warping the beam over time into an outward bowed shape. This warping can be unsightly, can lead to slight dimensional changes in the system""s rack structure, and can reduce the overall functionality of a push back rack system.
Previous rack systems have attempted to reduce this bowing effect by providing for multiple attachments between cart tracks and interior structural members. In such designs, the ends of each track are then bolted or welded to the beam so that the interior structural members assist the tracks in bracing against cart collisions. Such designs require the addition of at least one angle assembly at each separate interconnection point between the tracks and interior structural members, significantly increasing the system""s cost. When a cart collides with a beam, the combined angle assemblies disperse compression load forces at right angles from the tracks to vertical support members, significantly reducing the system""s overall ability to support the beam and to prevent warping.
Other systems have included the incorporation of clamping plates for providing connections between the rails and beams. These systems have suffered from many of the same limitations as simple bolted or welded designs due to compression forces associated with angular bracing and due to the structural limitations of the beams. In a number of designs, heavier beams or more rigid beam materials have been used to compensate for such limitations in the implemented bracing systems. While these designs have been successful in delaying or reducing the effects of warping, they too ultimately permit warping to occur after extended periods of usage.
The present invention is a beam and tension rod arrangement for use with a push back storage rack system. In a push back rack system, a front beam extends between two front vertical uprights across the loading position of one or more cart lanes. The front beam is divided into a middle portion and first and second ends and may also have a rectangular cross section for increased rigidity. The front beam may also have a vertically planar back surface positioned toward the cart lane and a vertically planar front surface positioned away from the cart lane.
One or more structural angles brackets may be positioned on the front beam""s back surface near the beam""s middle portion and extend partially along the length of the front beam toward the beam""s first and second ends. An interior structural cross support extends between two interior vertical uprights that are located at points along the length of each cart lane. The interior structural cross support has first and second ends which connect to the adjacent interior vertical uprights. Diagonal tension rods extend from each end of the interior structural cross support to points on the front beam""s structural angles brackets that are adjacent to the beam""s middle portion.
In some embodiments of the invention, the tension rods have hooked ends which extend through holes in the beam""s structural angles brackets. The tension rods may also have threaded ends which extend through the interior structural cross support and which permit variable tightening of the tension rods between the beam and structural cross support with a nut and washer combination.
When a loaded cart enters the loading position of the cart lane, the cart collides with the front beam. The majority of the collision forces are directed toward the middle portion of the front beam, which tends to flex under the strain of the collision. However, the front beam exerts diagonal tension forces on the tension rods between the beam and the interior structural cross support. The diagonal tension rods serve to brace the front beam against such flexing, transferring much of the impact strain to the interior structural cross support. In doing so, the tension rods tend to more evenly distribute the impact forces among the system""s multiple interior vertical uprights. The arrangement distributes impact forces relying largely on linear tension rather than on angular compression, making the invention better suited to brace the front beam during collisions. Some embodiments have a front beam with rectangular cross sections which provide additional resistance to the impact force due to the increased structural rigidity resulting from their shape. Both separately and in combination, the elements of the beam and tension rod arrangement provide heightened resistance to beam warping even after extended use.
Those skilled in the art will realize that this invention is capable of embodiments which are different from those shown and described below and that the details of the structure of this beam and tension rod arrangement can be changed in various manners without departing from the scope of this invention. Accordingly, the drawings and description below are to be regarded as illustrative in nature and are not to restrict the scope of this invention. The claims are to be regarded as including such equivalent front beam and tension rod arrangements as do not depart from the spirit and scope of the invention.